I just installed a DORAN wireless system. (I think they just bought out another company, maybe Pressure Pro) It goes for about $900 for a 12 wheel system. I'm 42 foot with a tag. There's an additional repeater that goes in the rear closet so you don't have worry about not getting the signal from the rear of your tow vehicle, a problem I had with the last system, which I had to return. You can also temporarily shut down the tow vehicle info on the monitor so when you drive somewhere without your tow vehicle the monitor isn't constantly alerting you that there is no air pressure in the tow vehicle tires!!
Hope this helps,
Jim
2007 Allegro Bus
Full Timing since 8/2007